The present invention relates generally to treatment of industrial wastes, and more particularly to microwave assisted cleaning and reclamation of oily metallic industrial wastes.
Several industrial processes produce oily mixed wastes. One example is hot strip rolling steel mills. Cooling water from these mills generally contains oily metallic particles. Typical treatment processes for these wastes use tanks and chemicals for flocculating, settling, thickening, de-watering, and stiffening to produce concentrated waste sludge.
FIG. 1 shows a block diagram of a typical treatment plant for processing oily cooling water from a hot strip rolling mill. The waste effluent enters a rapid mix tank 20, as shown by arrow 22, where it is mixed with an anionic polymer. From there, it proceeds through conduits 24 to clarifying tanks 26, as shown by arrows 25, where oil is skimmed off, as shown by arrows 28, and water is removed, as shown by arrows 30, and directed to a wet well 32. From the wet well 32, the water is directed through pressure filters 34, a cooling tower 36, and into a cold well 38, as shown by arrows 33, 35 and 37, to provide a source of cooling water for the mill again.
The remaining waste 39 from the clarifying tanks 26 is directed through conduits 40 to thickening tank 42, as shown by arrows 41, where anionic and/or cationic polymers, and/or sulfuric acid are added. The thickened waste 44 is then directed through conduit 46 to drum filter 48, as shown by arrow 47, and finally deposited as a waste sludge cake in receptacle 50, as shown by arrow 49.
The sludge volume is typically approximately ⅓ water, ⅓ oil, and ⅓ iron metal and iron oxides, to which lime is added for stiffening. The waste sludge is typically disposed of in a special landfill or trucked to a special processing plant external to the producing, company.
A typical hot strip rolling mill can generate 50 tons of sludge per day and more than 7,000 tons per year. The costs associated with production and disposal of this sludge are significant.
Moreover, conventional water treatment processes are time consuming, and plant equipment is very bulky, requiring extensive housing space at mill facilities. Also, as land fills reach capacity, the cost of disposal of mill waste sludge can be expected to increase.
Accordingly, there is a need for faster, smaller and more economical industrial waste water treatment systems.
There are many known processes for the separation of oil and water emulsions. These processes are commonly referred to as emulsion cracking. Emulsion cracking typically needs the addition of heat and frequently requires deemulsifying chemical agents. Processing times using gravity settling methods often require 4 to 24 hours for better than 90% separation.
Recently, oil/water emulsion cracking systems using microwave energy have been successfully field tested and are currently being developed, mainly for the petroleum industry. Microwave emulsion cracking systems are compact and have demonstrated rapid, continuous, processing at flow rates to beyond 50 gallons-per-minute (gpm), through the use of flow through microwave applicators. Efficient microwave processing typically requires only a 20xc2x0 C. process temperature rise and uses power, for example, at an 8 to 12 kilowatts per gallon per minute (kW/gpm)power processing rate. For some applications, microwave emulsion cracking has the added benefit of not requiring the addition of chemicals.
While these methods may improve the separation of oil-water emulsions, they do not address the distinct problem of additionally separating oil from metallic solids frequently present in industrial waste effluents, such as cooling water from hot strip rolling mills. Accordingly, it is an object of the present invention to provide a method for treating industrial wastes containing oily metallic solids by separating a waste into its various components for reclamation and reuse, thereby significantly reducing or eliminating waste sludge. It is also an object of the present invention to provide waste water treatment process equipment that is faster and more compact than that presently typically used.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the claims.
The present invention provides a process and apparatus for cleaning and reclamation of an industrial waste containing oily metallic solids by magnetically concentrating the oily magnetic solids, mixing the concentrated solids with a chemical release agent, applying microwave radiation to the mixture, and separately collecting the clean metallic solids and recovered oil components.